// Hex JavaScript decoder
// Copyright (c) 2008-2013 Lapo Luchini <lapo@lapo.it>
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

/*jshint browser: true, strict: true, immed: true, latedef: true, undef: true, regexdash: false */
var decoder;
export var Hex = {
    decode: function (a) {
        var i;

        if (decoder === undefined) {
            var hex = '0123456789ABCDEF';
            var ignore = ' \f\n\r\t\xA0\u2028\u2029';
            decoder = {};

            for (i = 0; i < 16; ++i) {
                decoder[hex.charAt(i)] = i;
            }

            hex = hex.toLowerCase();

            for (i = 10; i < 16; ++i) {
                decoder[hex.charAt(i)] = i;
            }

            for (i = 0; i < ignore.length; ++i) {
                decoder[ignore.charAt(i)] = -1;
            }
        }

        var out = [];
        var bits = 0;
        var char_count = 0;

        for (i = 0; i < a.length; ++i) {
            var c = a.charAt(i);

            if (c == '=') {
                break;
            }

            c = decoder[c];

            if (c == -1) {
                continue;
            }

            if (c === undefined) {
                throw new Error('Illegal character at offset ' + i);
            }

            bits |= c;

            if (++char_count >= 2) {
                out[out.length] = bits;
                bits = 0;
                char_count = 0;
            } else {
                bits <<= 4;
            }
        }

        if (char_count) {
            throw new Error('Hex encoding incomplete: 4 bits missing');
        }

        return out;
    }
};
